package jjn.acwing;

import java.util.Scanner;

/**
 * @author Jjn
 * @since 2023/7/22 11:28
 */
public class Acwing604 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        while (scanner.hasNext()) {
            double nextDouble = scanner.nextDouble();
            System.out.printf("A=%.4f\n", nextDouble * nextDouble * 3.14159);
        }
    }
}
